Apparatus for drying and simultaneously cooling the white sugar coming from a centrifuge station



Jan. 18, 1966 H KAMP 3,229,383

APPARATUS FOR DRYING AND SEMULTANEOUSLY COOLING THE WHITE SUGAR COMING FROM A CENTRIFUGE STATION Filed Jan. 21, 1963 United States Patent @flfrce 3,229,383 APPARATUS FOR DRYENG AND SIMULTANE- ()USLY COOLING THE WHITE SUGAR COMING FRQM A CENTRHUGE STATION Heinrich Kamp, Krefel-d-Bockum, Stippergath, Germany,

assignor to Buttner-Werke Aktiengeselischaft, Krefeid- Uerdingen, Germany Filed Jan. 21, 1963, Ser. No. 252,815 Claims priority, application Germany, Feb. 2, 1962, B 65,791 8 Claims. ((11. 34-65) The invention relates to apparatus for drying and simul taneously cooling white sugar coming from a centrifuge station.

Such apparatus is known which comprises a housed annular tray-like drier with a preliminary drying and agitating drum connected thereto in advance thereof, in which drum the still moist sugar mass from a centrifuge is prevented, by the constant movement imparted thereto, from caking together in lumps, While the tray drier provides a gentle finishing treatment for the sugar.

According to my United States Patent No. 2,869,249, the housing of the annular tray drier is divided into communicating upper drying and lower cooling zones so that cooling air may flow upwardly through the cooling zone and, thereafter, being partially warmed, passes into the drying zone, equipped within its interior with a heating means which further heats the said air to the necessary drying temperature. This air is discharged from the drying zone and passes into the preliminary drying drum for the initial drying of the sugar; and then this same moistureladen air is returned to the drying zone of the tray drier where it mixes with the air from the cooling zone of the tray drier and re-heated by the heating means within said drying zone.

The disadvantage of such known apparatus is that its fixed scheme of operation, as regards the conduction of the drying and cooling air, does not enable the method of operation to be adapted to varying initial moisture contents of the sugar. It is known that according to the method of operation of the centrifuge, for example whether covered with water or steam, the moisture content of the sugar can fluctuate between 0.5 and 2% and the natural sugar temperature can fluctuate between 75 and 40 C. Nevertheless, the condition exists that the sugar must be uniformly dried to a final moisture content of, for example, 0.03% to 0.05% and cooled for example to 30 C. However, it is not possible for these conditions to be satisfied with the known apparatus. It is an additional disadvantage with the known apparatus that the production of the hot air necessary for the drying must be accomplished by the heater battery installed within the drying zone of the tray drier. In this connection, there is the danger of powdered sugar being deposited on the hot pipes, whereby a more or less thickening layer of burnt sugar is formed on these pipes, and this layer impairs the transfer of heat from the heater pipes to the circulated air. A further disadvantage is that the moisture laden air, which has passed through the preliminary drum drier, is returned to the drying zone of the tray drier.

The present invention is an improvement upon such prior art apparatus as above outlined and has for its object a more flexible apparatus for the treatment of sugar batches, having widely varying moisture content and tem perature ranges, and which can be adjusted so that the resulting end product has a more uniformly normal moisture content and temperature at the end of the treatment, resulting in a more acceptable marketable product.

According to the present invention, the improvement comprises an apparatus for drying sugar having superposed tray-like members rotatable on a vertical axis en- Patented Jan. 18, 1966 closed in the housing, which housing is subdivided into a separate upper drying zone and separate lower cooling zone, in each of which heating air and cooling air is circulated, respectively, and exhausted controllably to the atmosphere; a preliminary drying and agitating drum discharging the sugar into the drying zone of the tray drier; an air-heater positioned to discharge fresh heated air into the sugar discharge end of said drying drum and traverse said heated air counter to the flow of the sugar mass in said drum, which air is exhausted controllably to the atmosphere; controllable duct means connecting said air-heater directly to the drying zone of the tray-drier, and/ or connecting to a separate second air heater to the drying zone, without passing the heated air through said drying drum; a port in the cooling zone of said housing for omitting cooling air to said cooling zone and a valve by-pass conduit connecting said port to the drying zone of said tray heater, whereby only fresh heated air of proper temperature (and not laden with moisture of prior treatments) may be supplied into said drying zone in controlled amounts and fresh cooling air may be supplied to the cooling zone simultaneously, and whereby the drying zone may be converted into an additional cooling zone by shutting off the heated air thereto and directly supplying fresh cooling air thereto independently of the air supplied to the cooling zone, this latter being advantageous when sugar from the centrifuge is less moist but very hot.

The superposed trays may be annular disc-like members surrounding and carried by an open frame rotatable about its vertical axis and the drying zone of the tray drier may be separated from the cooling zone thereof by a fixed partition plate which has an opening for the transfer of the sugar onto an annular disc situated beneath the plate only in the region of a stripper device for the material. The closing of the space within the open framework between the annular discs in the cooling zone and those in the drying zone is sealed by a partition plate fixed within said frame and positioned to cooperate with said other fixed partition plate.

One construction of the invention will now be described by Way of example with reference to the accompanying drawing, in which:

FIG. 1 is a diagrammatic view, partly in section, of an arrangement according to the invention; and

FIG. 2 is a section on the line AB in FIG. 1.

The drawin shows a housing 1 of an annular tray drier with a multiplicity of superposed tray-like annular discs 2 surrounding and fixed on a vertical rotary ring frame 3 and spaced one above the other in shelf-like arrangement. The annular discs each formed with a plurality of radially spaced slots 4, through which the sugar is transferred onto the next lower tray-like annular disc by means of an overlying stripper device 5 having one end secured to the adjacent wall of the housing 1 (FIGS. 1 and 2). While only one such stripper device is shown in the drawing, it is to be understood that one such stripper device 5 is arranged above each disc, so that the sugar supplied at an inlet 6 remains on each disc 2 for most of one revolution thereof and gradually travels successively through the complete arrangement of discs and is discharged at an outlet 7. The vertical rotary frame 3 may be of the cage-type shown in my aforesaid United States patent, or may be a foraminated or perforated cylindrical wall as shown in FIG. 1 hereof. The rotary frame 3 is supported in position by a vertical shaft 10 extending axially therethrough and is journalled in the ends of said frame so that the frame and the shaft may rotate independently of the other. The upper end of the shaft 10 is journalled in the housing 1 as at 10a and its lower end in a base-block 1%. Both the frame 3 and the shaft 1% are driven by a motor means not shown.

The annular disc drier has an upper drying zone D and a lower cooling zone C which are separated by a fixed annular partition plate 8 which is part of the housing 1 and upon which drops the sugar from the lowermost disc in the drying zone. This fixed plate 8 is formed with an opening 4a through which the sugar thereon is transferred onto the annular disc located beneath it by means of a stripper device 5a overlying the plate 8 and connected at one end to the rotary frame 3. The internal space within the rotatable frame 3 is divided by an imperforated partition plate 9 which is mounted fixedly to and transversely of the rotary ring frame 3 in substantially the same location as the plate s to prevent air communication within the frame 3 between the cooling zone C and the drying zone D. Fans 11, which are mounted on and rotated by the shaft 16, provide for a uniform circulation of the cooling air and heating air through the layers of sugar at least one of said fans being disposed in each of the zones C and D. The cooling zone C of the housing 1 has an intake-port 24 through which atmospheric or cooled air is admitted to said zone. A cooling air duct 12, having a throttle-valve 12a therein, is arranged laterally of the cooling zone and communicates the cool air intake-port 24 with the drying zone D, preferably immediately above the partition 8, as at 1212. Exhaust air pipes 13 and 14 lead from the drying and cooling zones, respectively, of the annular disc drier to the atmosphere by way of a suction fan 15 and a wet dust extractor 16. These exhaust air pipes are connected into a header conduit 21 in advance of intake side of the suction fan 15.

A drying drum 17 is on the input side 6 of the housing 1 and has an air exhaust housing 18 and a supply worm 19 for feeding the wet sugar from a centrifuge station (not shown) into one end of the drum 17. A suitable air-heater 20 is positioned at and in communication with the sugar discharge end 17a of the drum 17. Hot air brought to the required temperature in the air heater 20, travels through the drying drum in counter-current to the flow of the sugar through the drum 17. From the air exhaust housing 18, the exhaust header air conduit 21 leads to atmosphere by way of the suction fan 15 and the dust extractor 16. The drying zone D of the annular disc drier is connected to the air heater 28 by a pipe conduit 22 which conduit projects into the heater and diverts a portion of the air heated in the air heater directly into the drying zone of the annular disc drier. Obviously, the air heater 20 must be so designed that it can supply the necessary quantity of hot air for both the drying drum 17 and the drying zone D of the annular disc drier. However, in certain situations it may be desirable to a provide separate air heater 25, which is connected by a conduit 25a to the hot air pipe conduit 22 leading to the drying zone of the annular disc drier.

In other situations, it may also be expedient for the air exhaust housing 18 of the drying drum 17 to be connected by a by-pass pipe 22a to the hot air pipe 22, so that some or all of the exhaust air of the drying drum may be conducted into the drying zone D of the annular disc drier.

Of course, it is to be understood that, when the conveyance of heated air to the drying zone D is properly performed by either one of the three arrangements above described and shown, the others may be rendered inoperative by suitable valve means or may supplement each other, or may be omitted from the system. However, the first arrangement described, employing the heater 20 and the conduit 22, is preferred. Each of the pipes or ducts 13, 14, 21, 22, 22a and 25a is provided with a throttle valve 23 so that it is readily possible for the pipes or ducts to be partly or completely closed.

The sugar first of all travels through the drying drum in which, due to the slow rotation of the drum, the mass of sugar is kept in constant motion, so that no agglomerates can be formed. Since the crystal sensitivity of the sugar increases with the increasing extraction of moisture, the annular disc drier is provided for the gentle final treatment. The air heated in the externally disposed air heater Ztl serves exclusively for heating the entire arrangement. By the present arrangement of this invention, no heaters are provided within the housing of the disc-drier itself, thus eliminating the drawbacks mentioned above while, at the same time, giving the additional advantages of obtaining a more sensitive and responsive control over wider conditions of the wet sugar mass to be treated.

On the assumption that the sugar has an initial moisture of 2% and a natural temperature of 40 C., the following air supply scheme is for example employed:

By opening the throttle valve 23 in the hot-air pipe conduit 22, hot air is conveyed from the air heater 20 directly into the drying zone of the annular disc drier, the valve 12a in the cooling air supply duct 12 being closed as will the valves 23 in conduits 22a and 25a if employed. In this case, an intensive drying of the sugar takes place in both the drying drum and in the drying zone of the annular disc drier. Beneath the plate 8 in the cooling zone C, the annular disc drier serves for cooling the sugar. The cooling air supplied through the inlet port 24 is discharged into the cooling zone C and is exhausted therefrom through the duct 14 after it has acted on the sugar.

However, based on the assumption that the sugar only has an initial moisture content of 0.5% and a natural temperature of for example 75 C., then the following procedure is used:

The throttle valve 23 in the conduit 22 is closed as are the valves 23 in conduits 22a and 25a, if the latter are employed. Therefore no hot air reaches the drying zone D of the annular disc drier, so that the latter is used entirely for the cooling of the sugar. For this purpose, the throttle valve 12a in the cooling air supply duct 12 is opened, thus allowing cool air to pass not only into the cooling zone C but also through conduit 12 into the drying zone D as well.

It is obviously possible to dispense with the cooling air supply duct 12 and to introduce the cooling air through the cooling zone into the drying zone, for example, by the fixed plate 8 being provided with an opening which can be wholly or partially closed by a slide member.

It is quite evident that the air supply devices can be varied, for example, when the initial moisture content and the natural temperature of the sugar are between the said values.

I claim:

1. In an apparatus for drying and cooling continuously moist hot white sugar coming from a centrifuge station, wherein there is an initial drying drum receiving said sugar from said station for a preliminary drying treatment and passing said sugar therethrough and therefrom to a rotary tray-drier including a plurality of disc-like members superposed over and above one another to form trays to retain said sugar, and a housing for said tray-drier having an inlet for delivering said sugar to the uppermost of said trays and having an outlet for discharging the dried and cooled sugar therefrom, means for rotating said trays, and means for transferring the sugar downwardly from one tray to another tray during the rotation of said trays; the improvement comprising means dividing said traydrier and its housing into an upper drying zone, devoid of a heating means and having air ingress and egress openings, and into a lower cooling zone, having an air ingress opening open to fresh cooling air and an egress opening; an air exhausting means connected to said egress openings to draw air into, through and from said zones of the tray drier and exhausting the same from the apparatus; an airheating means having its intake open to fresh atmospheric air; air duct means connecting the discharge side of said air-heating means to the sugar discharge end of said dry ing drum and connecting the sugar intake end of the drying drum with said exhausting means and, further, air

duct means connecting said air-heating means directly with the air ingress opening of the drying zone of said tray-drier without passing through the drying drum; and air-valve control means in each of said duct means for controlling the passage of air therethrough.

2. An apparatus as claimed in claim 1, comprising an exhaust housing associated with the sugar intake end of the drying drum, and a valve controlled air by-pass conduit, said exhaust housing being connected by said air bypass conduit to said air duct means connected between said drying zone and said heater means.

3. An apparatus for drying and cooling moist hot white sugar as set forth in claim 1 further characterized by a valve-controlled air by-pass duct connecting the cool air ingress opening of the cooling zone with the drying zone of the tray-drier, whereby, upon closing the valve-controlled duct from the airheating means to the drying zone of said tray-drier and opening said by-pass duct, the entire tray-drier can be converted into a cooling zone.

4. An apparatus for drying and cooling moist hot white sugar as set forth in claim 1, wherein the air-heating means comprises an air-heater communicating with said initial drying drum to deliver fresh heated atmospheric air thereto counter to the flow of said sugar therethrough and, further, connected to said drying zone of the tray-drier, which latter connection bypasses the initial drying drum.

5. An apparatus for drying and cooling moist hot white sugar as set forth in claim 1, wherein the connections between the egress openings of the drying and cooling zones of the tray-drier and said exhausting means are provided with valves, respectively, for controlling the air exhausted from said zones.

6. An apparatus for drying and cooling moist and hot white sugar as set forth in claim 1, wherein the air-heater means comprises two separate air-heaters, one connected to the initial drying drum to deliver heated air thereto and the second of said heaters being connected to the drying zone of said tray-heater.

7. An apparatus for drying and cooling moist hot white sugar as set forth in claim 6, wherein the second of said air heaters has its discharge side in valve controlled communication with the air duct means connecting the first air-heater with the drying zone of the tray-drier.

8. An apparatus for drying and simultaneously cooling moist hot white sugar coming from a centrifuge station, the said apparatus comprising a tray-drier including a housing therefor having an inlet for moist sugar and an outlet for dried sugar, a ring frame in said housing, a plurality of annular discs arranged one above the other on and surrounding said frame and having slots therein to transfer said sugar from one disc to another disc, means for rotating said discs, a drying zone and a cooling zone in said housing; a cool air supply means communicating with the cooling zone, a cool air duct connected to deliver cooling air directly frorn said cool air supply means into said drying zone and having a control valve therein; a fixed annular plate separating said zones and having slots therein, a stripper device located in the region of said fixed plate for transferring sugar through said slots in said plate onto an annular dis-c situated therebelow; a second fixed plate within said ring-frame cooperating with said first mentioned plate to seal off the internal space within said frame; an initial drying drum disposed in advance of said tray-drier and having a sugar intake opening and a sugar discharge opening, said discharge opening being connected to said sugar inlet of said housing; an air-heater arranged at the sugar discharge portion of said drying drum and communicating With said drying drum for heating the latter; a separate valve controlled air duct communicating said drying zone in said housing directly with said air-heater; an air exhaust housing associated with the drying drum; and a suction exhausting means connected to said exhaust housing and connected to the cooling and drying zones of said tray-drier.

References Cited by the Examiner UNITED STATES PATENTS 1,502,858 7/1924- Little W 3465 X 1,517,788 12/1924 Little 3465 2,869,249 1/1959 Kamp 34-65 MORRIS O. WOLK, Primary Examiner. 

1. IN AN APPARATUS FOR DRYING AND COOLING CONTINUOUSLY MOIST HOT WHITE SUGAR COMING FROM A CENTRIFUGE STATION, WHEREIN THERE IS AN INITIAL DRYING DRUM RECEIVING SAID SUGAR FROM SAID STATION FOR A PRELIMINARY DRYING TREATMENT AND PASSING SAID SUGAR THERETHROUGH AND THEREFROM TO A ROTARY TRAY-DRIER INCLUDING A PLURALITY OF DISC-LIKE MEMBERS SUPERPOSED OVER AND ABOVE ONE ANOTHER TO FORM TRAYS TO RETAIN SAID SUGAR, AND A HOUSING FOR SAID TRAY-DRIER HAVING AN INLET FOR DELIVERING SAID SUGAR TO THE UPPERMOST OF SAID TRAYS AND HAVING AN OUTLET FOR DISCHARGING THE DRIED AND COOLED SUGAR THEREFROM, MEANS FOR ROTATING SAID TRAYS, AND MEANS FOR TRANSFERRING THE SUGAR DOWNWARDLY FROM ONE TRAY TO ANOTHER TRAY DURING THE ROTATION OF SAID TRAYS; THE IMPROVEMENT COMPRISING MEANS DIVIDING SAID TRAYDRIER AND ITS HOUSING INTO AN UPPER DRYING ZONE, DEVOID OF A HEATING MEANS AND HAVING AIR INGRESS AND EGRESS OPENINGS, AND INTO A LOWER COOLING ZONE, HAVING AN AIR INGRESS OPENING OPEN TO FRESH COOLING AIR AND AN EGRESS OPENING; AN AIR EXHAUSTING MEANS CONNECTED TO SAID EGRESS OPENING; AN DRAW AIR INTO, THROUGH AND FROM SAID ZONES OF THE TRAY DRIER AND EXHAUSTING THE SAME FROM THE APPARATUS; AND AIRHEATING MEANS HAVING ITS INTAKE OPEN TO FRESH ATMOSPHERIC AIR; AIR DUCT MEANS CONNECTING THE DISCHARGE SIDE OF SAID AIR-HEATING MEANS TO THE SUGAR DISCHARGE END OF SAID DRYING DRUM AND CONNECTING THE SUGAR INTAKE END OF THE DRYING DRUM WITH SAID EXHAUSTING MEANS AND, FURTHER, AIR DUCT MEANS CONNECTING SAID AIR-HEATING MEANS DIRECTLY WITH THE AIR INGRESS OPENING OF THE DRYING ZONE OF SAID TRAY-DRIER WITHOUT PASSING THROUGH THE DRYING DRUM; AND AIR-VALVE CONTROL MEANS IN EACH OF SAID DUCT MEANS FOR CONTROLLING THE PASSAGE OF AIR THERETHROUGH. 